1. Field of the Invention
This invention relates to a method and an apparatus for the vapor phase growth of a thin film such as silicon on a semiconductor crystal substrate.
In the production process of a semiconductor crystal thin film in the prior art, a reaction vessel has been made of only a quartz glass in order to establish metal contaminant free environment over the entire reaction zone. In the case of a horizontal type vapor phase growth apparatus, a reaction vessel of which length direction is horizontal and which has a rectangle cross section is made of a quartz glass and a transfer port for replacing a substrate had to be mounted at the upstream side or the downstream side of a substrate setting position in the reaction vessel.
In the reaction vessel of a horizontal type vapor phase growth apparatus, polycrystal particles which are produced by a side reaction of raw material reactant gases are used to accumulate at the reaction vessel wall at the downstream side of the substrate setting position, therefore, when a loading and unloading of a substrate is performed from the downstream side of the substrate setting position, the polycrystal particles exfoliated from the wall adhere to a transferring substrate and a vapor phase growth processed thin film surface, then ratio of a surface defect increases. Accordingly, the loading and unloading of the substrate has to be managed at the upstream side of the substrate setting position.
As is shown in FIG. 10, in the case of the loading and unloading of the substrate 41 from the upstream side of the substrate setting position, a gas supply part 23 through which a mixture gas 33 consisting of a raw material gas 31 (source gas containing a necessary quantity of a dopant) and a carrier gas 32 is arranged close to a transfer port 27 through which the substrate 41 is loaded and unloaded. For example, a nozzle 22 introducing the mixture gas 33 is vertically mounted to a upside wall 21a of the reaction vessel 21, and the transfer port 27 is mounted at an end wall 21e of the upstream side of the reaction vessel 21.
One of the roles of the nozzle 22 is adjustment of flow rate or concentration of the mixture gas 33. For example, in order to establish homogeneity of the thickness and resistivity of the thin film 42 within a surface of the substrate as shown in FIG. 11, a right side supply port 24, a central supply port 25, and a left side supply port 26 are mounted in the reaction vessel 21, through these ports raw material gas has been supplied with adjusting properly the concentration of a source gas and a dopant gas in a width direction of the reaction vessel.
The nozzle 22 consisting of gas supply ports 24 to 26 in FIG. 10 is mounted vertically to the upside wall 21a, and through the nozzle 22 the mixture gas 33 is introduced to the reaction vessel 21, then just after introduction of the mixture gas 33, a vortex 34 is formed by the mixture gas 33. Therefore, the concentration distribution settled at the nozzle part will be equalized by a long time of stagnation of the raw material gas 31 in the vortex 34 and moreover by a diffusion and stirring of gas flow, though the concentration distribution preliminary formed in the width direction of the reaction vessel at the gas supply port 24 to 26, and it is difficult to establish the homogeneity of the film thickness and the resistivity above said. In FIGS. 10 and 11, 21b, 21c and 21d are a bottom wall, a right side wall and a left side wall, respectively.